Current inlet member



Oct. 31, 1961 A. BOL ETAL 3,006,984 CURRENT INLET MEMBER Filed Nov. 10, 1959 INVENTOR 0.J.M. VANDE LAAN P.J.M. TACKEN 6. E443 BY A. 80L

AGENT l J i T The invention relates to a current leading-in member comprising one or more conductors, which are secured in a gastight manner in a sintered, glasslike body, which is surrounded by a metal ring, of which the metal has a higher expansion coefiicient than the glasslike body.

It is known that such leading-in members are capable of withstanding heavy mechanical and thermal thrusts.

It is also known that such inlet members can be manufactured in a large size, to which end cheap metals such as steel can be employed, if the expansion coefiicient of the glasslike body matches more closely that of the metal. This may be achieved by manufacturing the body of about 10% by weight of glass powder and 60% by weight of magnesia powder. The magnesia particles should in this case not be so fine that the glass can no longer penetrate into the space between them. The smallest size is about a few tenths of a millimetre. The temperature during sintering of the mass must not be so high that the ceramic particles dissolve in the glass, since then the expansion coeflicient would be afiected adversely.

It is furthermore known for use at very high frequencies and voltages to manufacture the glass mass from a mixture of glass powder and mica.

It has appeared, however, that in certain cases, in the event of great thermal or mechanical shocks, the known bodies may exhibit cracks in the glass-like mass.

From many experiments it has noW appeared that the mechanical and thermal strength of such current lead-in members, in which the sintered, glasslike mass consists of a mixture of glass and ceramic powder, can be materially improved, if the size of the ceramic particles is less than 1., whilst the quantity of ceramic material lies between 0.2 and 5% by weight. Use is preferably made of ceramic particles of la.

It has been found that the inlet members have greater strength according as the melting temperature of the glasslike mass is higher. The choice of this material is restricted by the fact that the diiference between the expansion coefiicients of this material and of the metal must lie within certain limits. The expansion COCfllClBDt of the metal of the external ring must, as a rule, exceed that of the glasslike body by about 25%.

It appears that the influence of ceramic particles such as A1 0 (alundum), phosterite (2MgO.SiO or titanic oxide (TiO) on the melting temperature is reduced according to the particle size increases, provided the temperature is not raised to an extent such that the particles dissolve in the glass, since the expansion coeflicient would then be changed to an inadmissible extent.

The invention will now be described more fully with reference to a drawing and one embodiment.

Referring to the drawing, of which the figure shows a definite embodiment of a current inlet member, reference numeral 1 designates the current supply conductor, 2 the glasslike material and 3 the external metal pressure ring. Instead of one supply conductor use may be made of any number of conductors.

3,006,984 Patented Oct. 31, 1961 In a known embodiment powder of a species of hard glass consisting of:

69.5% by weight of SiO 0.6% by weight of Li O, 7.2% by weight of Na O, 8.6% by weight of K 0, 10.8% by weight of BaO, 2.9% by weight of Sb O 0.2% by Weight of NiO, 0.1% by weight of Cr O 0.1% by weight of C00,

is moulded in a suitable shape with a binder of a synthetic resin solution, after which sintering is carried out at 700 C. for about 10 minutes, and the material is passed around the metal current conductors in the metal ring, the material being then melted at 950 C. for 5 minutes, after which cooling is performed at a rate of 0.5 to 1 C. per second.

In the embodiment according to the invention the aforesaid glass powder has added to it 5% by weight of A1 0 of which the particle size amounts to In. The sintering process may take place at 800 C. and the melting process at 1050 C. for the aforesaid periods. Cooling is also performed at a rate of 0.5 to 1 C. per second.

It is found that the expansion coeificients of the glass masses are substantially the same, but that the inlet member according to the invention has greater strength to mechanical and thermal shocks than the known members.

What is claimed is:

1. A current lead-in member comprising at least one conductor, a metal ring surrounding and spaced from the conductor, and a glass-like insulating material filling the space between the conductor and the ring, said glasslike material consisting essentially of a mixture of glass and between about 0.2 and 5% by weight of particles of ceramic material having a particle size smaller than 5 w 2. A current lead-in member as claimed in claim 1 in which the particles of ceramic material have a particle size of about 1 ,u..

3. A lead-in conductor as claimed in claim 1 in which the ceramic material is A1 0 4. A lead-in conductor as claimed in claim 1 in which the ceramic material is 2MgO.SiO

5. A lead-in conductor as claimed in claim 1 in which the ceramic material is TiO.

6. A lead-in conductor as claimed in claim 1 in which the glass has the composition:

69.5% by weight of SiO 0.6% by weight of Li O 7.2% by weight of Na O 8.6% by weight of K 0 10.8% by weight of BaO 2.9% by weight of Sb O 0.2% by weight of NiO 0.1% by weight of Cr O 0.1% by weight of C00.

References Cited in the file of this patent UNITED STATES PATENTS 2,408,468 Lyon Oct. 1, 1946 2,513,958 Omley July 4, 1950 2,669,808 Duncan Feb. 23, 1954 FOREIGN PATENTS 162,555 Australia Apr. 21, 1955 

